Power supply device performing voltage conversion

Abstract

In a power supply device, the controller outputs a control signal specifying a voltage value. The voltage conversion unit converts a first voltage to a second voltage in response to a control signal specifying a voltage value output from the controller. The voltage conversion unit converts the first voltage to a start voltage, as the second voltage, in response to a first control signal specifying a start voltage value output from the controller and further converts the first voltage to a target voltage, as the second voltage, in response to a second control signal specifying a target voltage value output from the controller. A transition period of time is intervened between generation of the start voltage and generation of the target voltage during which the controller outputs a third control signal specifying the intermediate voltage value between the start voltage value and the target voltage value.

What is claimed is: 
     
       1. A power supply device comprising:
 a first voltage generating unit configured to generate a first voltage; 
 a controller configured to output a control signal specifying a voltage value; and 
 a voltage conversion unit configured to convert the first voltage to a second voltage in response to a control signal specifying a voltage value output from the controller, and output the second voltage, 
 wherein the voltage conversion unit converts the first voltage to a start voltage, as the second voltage, in response to a first control signal specifying a start voltage value output from the controller and further converts the first voltage to a target voltage, as the second voltage, in response to a second control signal specifying a target voltage value output from the controller, 
 wherein a transition period of time is intervened between generation of the start voltage and generation of the target voltage during which the controller outputs a third control signal specifying the intermediate voltage value between the start voltage value and the target voltage value. 
 
     
     
       2. The power supply device according to  claim 1 , wherein the controller sequentially outputs control signals specifying voltage values that continuously vary from the start voltage value to the target voltage value in the transition period of time. 
     
     
       3. The power supply device according to  claim 1 , wherein the intermediate voltage value is closer to the target voltage value than an average of the start voltage value and the target voltage value. 
     
     
       4. The power supply device according to  claim 1 , wherein the controller outputs the first control signal specifying the start voltage value, the third control signal specifying the intermediate voltage value, and a second control signal specifying the target voltage value in said order in the transition period of time. 
     
     
       5. The power supply device according to  claim 1 , wherein the control signal includes a PWM signal having a duty cycle corresponding to the value of the voltage,
 wherein the voltage conversion unit converts the first voltage to the second voltage based on the duty cycle and outputs the second voltage. 
 
     
     
       6. The power supply device according to  claim 5 , wherein the voltage conversion unit includes:
 a resistor portion having a resistance value; and 
 a resistance changing unit configured to change the resistance value of the resistor portion based on the duty cycle. 
 
     
     
       7. The power supply device according to  claim 1 , wherein the voltage conversion unit comprises:
 a transformer including a primary side and a secondary side, and configured to induce an induced voltage across the secondary side when the primary side is oscillated; 
 a switching element connected to the primary side; 
 an output line connected to the secondary side, and configured to output the second voltage; 
 a voltage detecting unit configured to detect a determination voltage generated from the second voltage and determine whether a voltage difference between a reference voltage and the determination voltage is larger than a threshold value; and 
 a switch controller configured to control the switching element to reduce the voltage difference when the voltage difference is larger than the threshold value. 
 
     
     
       8. The power supply device according to  claim 1 , wherein the controller sequentially outputs control signals specifying values of the voltage that gradually vary from the start voltage value to the target voltage value.